Many modern aircraft, as well as other vehicles and industrial processes, employ gas turbine engines for generating energy and propulsion. Such engines include a fan, compressor, combustor and turbine provided in serial fashion and arranged along a central longitudinal axis. Air enters the gas turbine engine through the fan and is pressurized in the compressor. This pressurized air is mixed with fuel in the combustor. The fuel-air mixture is then ignited, generating hot combustion gases that flow downstream to the turbine. The turbine is driven by the exhaust gases and mechanically powers the compressor and fan via a central rotating shaft. Energy from the combustion gases not used by the turbine is discharged through an exhaust nozzle, producing thrust to power the aircraft.
Gas turbine engines contain an engine core and fan surrounded by a fan case, forming part of a nacelle. The nacelle is a housing that contains the engine. The fan is positioned forward of the engine core and within the fan case. The engine core is surrounded by an engine core cowl and the area between the nacelle and the engine core cowl is functionally defined as a bypass duct. The bypass duct is substantially annular in shape to accommodate the airflow from the fan and around the engine core cowl. The airflow through the bypass duct, known as bypass air, travels the length of the bypass duct and exits at the aft end of the bypass duct at an exhaust nozzle.
In addition to thrust generated by combustion gasses, the fan of gas turbine engines also produces thrust by accelerating and discharging ambient air through the exhaust nozzle. Various parts of the gas turbine engine generate heat while operating, including the compressor, combustor, turbine, central rotating shaft and fan. To maintain proper operational temperatures, excess heat is often removed from the engine (via oil coolant loops, including air/oil or fuel/oil heat exchangers) and dumped into the bypass duct airflow for removal from the system.
As compressed air travels downstream from the compressor, it passes through a pre-diffuser prior to entering the combustor. The pre-diffuser directs the airflow through passages with expanding areas, slowing the airflow and allowing for a more efficient combustion process. The pre-diffuser may include inner diameter and outer diameter walls connected by a plurality of struts. The passages are defined by the walls and struts.
As the gas turbine engine operates, various components may absorb different amounts of heat energy. This absorption, along with part location, build loading and part material, may cause different degrees of thermal expansion. This thermal expansion may cause stresses on certain gas turbine engine parts or locations, such as the leading edge of a strut, or the junction between a strut and an inner or outer diameter wall. Prior strut arrangements can adversely localize strains or hinder air flow through the passages.
Accordingly, there is a need for an improved pre-diffuser strut for a gas turbine engine.